The long-range objective of this project is to continue to study the mechanism by which surgical procedures or accidental trauma disrupt the neuroendocrine systems responsible for the control of water and salt balance. Five short-term projects are planned which will consist (1) of measuring the effect of plasma vasopressin levels of 4, 8, 16, 32, 64, and 128 micron U/ml created by step infusions of synthetic arginine vasopressin on total and compartmental renal blood flow in dogs as measured with Xenon133 washout technique, (2) of determining renal clearance of vasopressin by measuring plasma and urine vasopressin levels during experiment 1, (3) of obtaining more accurate data concerning the decay of vasopressin from plasma following intravenous unit impulse of vasopressin for use in network analysis of vasopressin secretory control system, (4) of creating a non-steady-state response pattern of vasopressin plasma levels in dogs using a computer controlled pump, and (5) to continue to develop antibodies for immunoassays of vasopressin and oxytocin. It is hoped that the information gained can be used to further reduce the mortality and morbidity of major surgical procedures and accidental injuries.